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Tuesday, July 2, 2013

Stretched vSphere Clusters for Disaster Avoidance (Metro vMotion)

A stretched cluster provides the
capability of balancing workloads between two datacenters. Workloads run
undisturbed and can be migrated between geographically close sites without the
need for sustaining an outage.

A stretched cluster is a single
cluster, typically set up over two sites that are separated by a distance of up
to 100 kilometers. With a stretched cluster, all disk writes are committed
synchronously at both the primary and secondary sites. Synchronous writes
ensure that data is always consistent regardless of the site from which the data
is being read.

A stretched cluster occupies a single
IP address space, so virtual machines can be migrated nondisruptively by
vMotion. The underlying technology of a stretched cluster is Metro vMotion.
Metro vMotion can be used to move a running virtual machine when the source and
destination ESXi hosts have a latency of more than 5 milliseconds round-trip
time latency. The maximum supported round-trip time latency between the two
hosts is now 10 milliseconds. Metro vMotion is available with the vSphere 5 Enterprise
Plus license.